Downhole telemetry system

ABSTRACT

A downhole telemetry system usable with a subterranean well comprises at least one pressure pulse generator, at least one pressure transmitter located in the internal tubular annulus in the well head and at least one pressure transmitter located in the casing annulus near the well. The system comprises a packer providing hydraulic isolation of the casing annulus and at least one transmitter located below the packer and responding to at least one physical quantity characterizing the bottom-hole zone. The system also includes a data encoder located below the packer to read out the transmitter located below the packer and to respond to at least one physical quantity characterizing the bottom-hole zone, a pressure pulse modulator to modulate pressure pulses generated by the pressure pulse generator, a surface-mounted data-collection unit to converts the output data of the transmitters and to provide a surface-mounted data decoder with data for analysis.

FIELD OF THE INVENTION

The invention relates to the field of geology, namely, to downholetelemetry systems.

A new embodiment of telemetry to be arranged over an acousticcommunications channel during the hydraulic fracturing activities issuggested for wells which are stimulated by using tubing. It has beenestablished that acoustic communications between the well head and thecasing annulus is arranged through a packer. The packer is not leaky,but is acoustically transparent. There is therefore an acoustic “wellhead/casing annulus” channel, so a pressure pulse can be sent from oneend of the channel and reliably received on the other end. Data areencoded through pulse modulation, using a modulator located below thepacker. This method does not require any additional equipment, exceptfor the above-mentioned modulator to be installed below the packer onthe outer side of the tubing.

BACKGROUND OF THE INVENTION

During the hydraulic fracturing activities, just like during thedrilling activities, the availability of real-time data obtained fromthe bottom hole (e.g. bottom-hole data) can be very useful. It is hardto install wire communications because an unprotected cable will be cutoff by the proppant-containing solution. Using a protected cable seemsto be an awkward option too. There are solutions suggesting that anoptical cable protected by coil tubing should be used, but thesesolutions imply new operational complications and increase the costs.The solutions associated with the use of a wired drill string may alsofail to handle the erosion problem which occurs due to the use ofproppant.

There are a number of hydraulic fracturing activities during whichtubing is inserted into a well (e.g. for protection of the well againstthe high pressure action). A packer is installed above the perforationsbetween the tubing and the casing string, thus forming the casingannulus. The casing annulus is filled with a low-viscosity fluid; thecasing annulus pressure is maintained by using a dedicated pump in orderto counteract the tubing pressure. So, the casing annulus is alow-attenuation acoustic waveguide. Embodiments of telemetry facilitieswhich use this channel have been considered in a number of patents(refer to Patents Nos. RU 2209964 dated Aug. 10, 2003, RU 2310215 datedOct. 7, 2005) and No. US 2005/0168349 published on Aug. 4, 2005.According to US 2005/0168349, the downhole telemetry system contains atleast one pressure pulse generator, at least one pressure transmitterlocated in the internal tubular annulus, at least one pressuretransmitter located in the casing annulus near the well, and a packer.

The main disadvantage of this system is the need to change the packersealing procedure, which complicates the process of taking measurementsby using the downhole telemetry system.

SUMMARY OF THE INVENTION

The problem to be solved by the claimed invention consists in thedevelopment of a downhole telemetry system providing a fast and accuratedownhole telemetry method.

The technical result achieved with the implementation of the claimedengineering solution consists in the development of a downhole telemetrysystem which eliminates the need to change the packer sealing procedureand, consequently, simplifies the process of taking measurements byusing the claimed system.

The said technical result is achieved due to the fact that the downholetelemetry system contains at least one pressure pulse generator, atleast one pressure transmitter located in the internal tubular annulusin the well head, at least one pressure transmitter located in thecasing annulus near the well, and a packer providing hydraulic isolationof the casing annulus. The system additionally contains at least onetransmitter which is located below the packer and which responds to atleast one physical quantity characterizing the bottom-hole zone, a dataencoder which is located below the packer and which reads out thetransmitter located below the packer and responding to at least onephysical quantity characterizing the bottom-hole zone, a pressure pulsemodulator which modulates pressure pulses generated by the pressurepulse generator and which is located in the casing annulus below thepacker, a surface-mounted data-collection unit which converts the outputdata of the transmitters and which provides the surface-mounted datadecoder with data for analysis.

In addition, the pressure pulse modulator can be designed in the form ofa valved chamber.

In addition, the pressure pulse generator is a mechanical device capableof increasing or decreasing the pressure. In addition, the physicalquantity which characterizes the bottom-hole zone and which thetransmitter located below the packer responds to is the pressure ortemperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is illustrated with a drawing where FIG. 1 shows thegeneral view of the downhole telemetry system, with the followingelements: Pressure pulse (1) generator, Fracturing fluid feed line (2),Pressure transmitters (3), Casing annulus line (4), Data-collection unit(5), Data decoder (6), Tubing (7), Packer (8), Pressure pulse modulator(9), Transmitters system and data encoder (10), Perforations (11) andHydraulic fracture (12).

This invention relates to downhole telemetry systems, i.e. to dataencoding and transmission systems which are used for encoding andtransmitting data from a well point located at a great depth and whichare designed to ensure that there is an internal tube, a casing annulusbetween this tube and the well wall, while the packer provides hydraulicisolation of at least two portions (the upper one and the lower one) ofthe casing annulus. The above-mentioned system consists of:

-   -   at least one pressure pulse generator (1) connected either to        the internal tubular annulus or to the casing annulus; this        generator is a mechanical device (such as a pump, a hydraulic        valve, etc.) capable of increasing or decreasing the pressure in        a certain point in the tube according to a certain schedule        (e.g. generating a pressure pulse of a certain type a certain        number of times per unit of time);    -   at least one pressure transmitter (3) which is designed to        measure the internal tubular annulus pressure, preferably (but        not compulsorily) in the well head, and at least one pressure        transmitter designed to measure the casing annulus pressure;    -   a packer (8);    -   at least one transmitter (10) which is located below the packer        and which responds to at least one physical quantity        characterizing the bottom-hole zone (e.g. to the pressure or        temperature);    -   a data encoder (10) which is located below the packer in the        well and which reads out the transmitter and converts these        readings into an encoded sequence of signals which control the        pulse modulator dynamics;    -   a pressure pulse modulator (9) which is preferably installed on        the outer side of the tubing (7) in the casing annulus below the        packer (8) and which is capable of changing amplitude        characteristics or phase characteristics of a pressure pulse        generated by the pressure pulse generator (1); this modulator is        a mechanical device which is controlled by the data encoder and        which changes the hydraulic characteristics (such as hydraulic        impedance) of the tube segment where this modulator is        installed;    -   a data-collection unit (5) which converts the output data of the        transmitters into analog or digital data and which preferably        (but not compulsorily) provides the synchronous data recoding        over all data-collection channels; this unit consists of a        sequence of electronic components which receive electrical        signals generated by the transmitters and which send these        signals to the input of an analog-to-digital or analog converter        providing the data decoder with data for analysis;    -   a surface-mounted data decoder (6) capable of converting a        modulated signal into data equivalent to at least that portion        of information, which is read out by the transmitters, with data        quality and quantity reductions being possible.

The pressure pulse modulator (9) can be designed in the form of a valvechamber to be installed on the section of the tubing (7), located belowthe packer (8), with the chamber valves being capable of opening and/orclosing at least one chamber port in order to connect the internalportion of the chamber to the well under the action of the signalarriving from the encoder.

Another embodiment of the pressure pulse modulator (9) can berepresented by a chamber or a set of chambers capable of expanding orcontracting, thus reducing or increasing the clearance between thetubing (7) and the well wall, under the action of the signal arrivingfrom the data encoder (10). The chamber or the set of chambers areinstalled on the section of the tubing (7), located below the packer(8).

Other embodiments of the pressure pulse modulator (9) are also possible.The selection of a specific embodiment will depend on the detailedgeometry of the annulus below the packer (8) and can be specified byacoustic filter specialists.

The signal is generated by the pressure pulse generator (1) connected tothe fracturing fluid feed line (2) and propagates at a high speed ofabout 1 km/s into the depth of the well where this signal is reflectedfrom the fracture system and from the bottom-hole zone and partiallypenetrates into the casing annulus zone where it undergoes some changesintroduced by the pressure pulse modulator (9) and passes through thepacker (8) and propagates upwards to be recorded there by the casingannulus pressure transmitter (3). Alternatively, the signal is generatedin the casing annulus and is recorded in the fracturing fluid feed line(2) on the surface. The pulse propagation path is the same in this case.

1. A downhole telemetry system usable with a subterranean wellcomprising: at least one pressure pulse generator connected either to aninternal tubular annulus or to a casing annulus, at least one firstpressure transmitter located in the internal tubular annulus in a wellhead to measure a pressure of the internal tubular annulus, at least onesecond pressure transmitter located in the casing annulus to measure apressure of the casing annulus, a packer providing hydraulic isolationof the casing annulus, at least one transmitter located below the packerto respond to at least one physical quantity characterizing abottom-hole zone, a data encoder located below the packer to read outthe at least one transmitter located below the packer, a pressure pulsemodulator adapted to change amplitude characteristics or phasecharacteristics of a pressure pulse generated by the pressure pulsegenerator and located in the casing annulus below the packer, asurface-mounted data-collection unit which converts an output data ofthe first and the second pressure transmitters into analog or digitaldata, a surface-mounted data decoder to receive and analyze the datafrom the surface-mounted data-collection unit.
 2. The system of claim 1,wherein the pressure pulse modulator has the form of a valve chamber. 3.The system of claim 1, wherein the pressure pulse generator is amechanical device capable of increasing or decreasing the pressure. 4.The system of claim 1, wherein the physical quantity which characterizesthe bottom-hole zone and which the transmitter located below the packerresponds to, is a pressure or a temperature.